The present invention relates to speed change gear devices, and particularly to a speed change gear device, in that by moving a gear switching rod, a switching rotary shaft can rotate so that the movable piece move the speed change disk. Thus the gears are switched to move forwards, move rightwards or to an idle gear.
Although the prior art speed change gear box can make the car to move forward, backward or in an idle gear condition. Moreover, the speed change gear box achieves the object by a complicated structure. Thereby, faults easily occur. Moreover, the prior art speed change gear box is difficult in manufacturing and longer manufacturing time is required. Thereby, there is an eager demand for improving this prior art defects.